1. Field of the Invention
The present invention relates to a thermal head, a method of manufacturing the thermal head, and a printer equipped with the thermal head.
2. Description of the Related Art
There has been conventionally known a thermal head for use in thermal printers, which performs printing on a thermal recording medium such as paper by selectively driving a plurality of heating elements based on printing data (see, for example, Japanese Patent Application Laid-open No. 2009-119850).
In the thermal head disclosed in Japanese Patent Application Laid-open No. 2009-119850, an upper substrate is bonded to a support substrate having a concave portion formed therein and heating resistors are provided on the upper substrate so that a cavity portion is formed in a region between the upper substrate and the support substrate so as to correspond to the heating resistors. This thermal head allows the cavity portion to function as a heat-insulating layer having low thermal conductivity so as to reduce an amount of heat transferring from the heating resistors to the support substrate, to thereby increase thermal efficiency to reduce power consumption.
A printer having the above-mentioned thermal head installed therein has a pressure mechanism for pressing thermal paper against a platen roller in a sandwiched manner. In order that heat of the surface of the thermal head be effectively transferred to the thermal paper, the thermal head is pressed against the thermal paper with an appropriate pressing force. Accordingly, the thermal head is required to have strength high enough to withstand the pressing force applied by the pressure mechanism.
Further, when the thermal paper is pressed against the surface of the thermal head by the platen roller, an air layer is formed between the thermal paper and the surface of the thermal head because of steps defined between the heating resistors and electrodes provided on both sides of the heating resistors. The heat generated by the heating resistors is hindered by the air layer from transferring to the thermal paper, which is inconvenient because thermal efficiency of the thermal head may decrease.
Further, the heat generated by the heating resistors diffuses also in the planar direction of the upper substrate via the electrodes. In particular, when the electrodes are thickened, the electrical resistance value of the electrodes can be reduced, but the amount of heat that diffuses via the electrodes is increased. Therefore, the conventional thermal head has a problem that high heat insulating performance exerted by the cavity portion cannot be fully utilized because the heat dissipates from the heating resistors in the planar direction of the upper substrate via the electrodes.